Using genomics to identify novel antimicrobials

There is a critical need in animal agriculture to develop novel antimicrobials and alternative strategies that will help to reduce the use of antibiotics and address the challenges of antimicrobial resistance. High-throughput gene expression analysis is providing new tools that are enabling the discovery of host-derived antimicrobial peptides. Examples of gene-encoded natural antibiotics that have gained attention include antimicrobial peptides such as human granulysin and its multi-species homolog, namely NK-lysin, which provide a protective response against a broad range of microbes and are a principal component of innate immunity in vertebrates. Both granulysin and NK-lysin are localised in cytolytic granules in natural killer and cytotoxic T lymphocytes. Host-derived NK-lysins that were first described in mammals are also found in avian species, and they have been shown to have antimicrobial activities that could potentially be used to control important poultry pathogens. Morphological alterations observed following chicken NK-lysin binding to Eimeria sporozoites and Escherichia coli membranes indicate damage and disruption of cell membranes, suggesting that NK-lysin kills pathogenic protozoans and bacteria by direct interaction. Genotype analysis revealed that chicken NK-lysin peptides derived from certain alleles were more effective at killing pathogens than those derived from others, which could potentially affect susceptibility to diseases. Although the host-derived antimicrobial peptides described in this paper may not, by themselves, be able to replace the antibiotics currently used in animal production, their use as specific treatments based on their known mechanisms of action is showing promising results.

Animal genomics in natural reservoirs of infectious diseases

Natural virus reservoirs such as wild bats, birds, rodents and non-human primates are generally non-model organisms that have, until recently, presented limited opportunities for in-depth study. Next-generation sequencing provides a way to partially circumvent this limitation, since the methods required for data acquisition and analysis are largely species-independent. Comparative genomics and other 'omics' provide new opportunities to study the structure and function of various biological systems of wild species that are otherwise out of reach. Genomes of natural reservoir hosts can help to identify dominant pathways of virus-host interaction and to reveal differences between susceptible and resistant organisms, populations and species. This is of great scientific interest and may also provide a resource for the rational design of treatments for viral diseases in humans and livestock. In this way, we will 'learn from nature' and one day apply this knowledge to create disease-resistant livestock or develop novel therapeutic and prevention strategies. Reservoir host genomics will also open up possibilities for developing novel vaccines for wildlife, aid in the development of new diagnostic platforms, and have broad implications for developmental and evolutionary biology. In this review, the authors focus on natural reservoir hosts of viral pathogens, although most of the discussion points should be equally applicable to natural reservoirs of pathogenic bacteria, fungi or other parasites.